Self-energizing disk brake for automotive vehicles

ABSTRACT

A self-energizing disk brake having a pair of thrust plates positioned within a stationary housing and between brake disks connected to a shaft to be decelerated. An actuating means to rotate the plates relative to each other to cause spherical balls trapped in complementary indentations in the facing surfaces of the plates to push the plates apart against the bias of a spring means into frictional engagement with the brake disks. Centering cams and lugs on the plates are capable of selective engagement with guide surfaces and projections formed on the housing. The cams and lugs are provided with yieldable vibration dampening elements having a low coefficient of friction to minimize the axially directed forces resisting separation of the plates.

United States Patent Powilleit [5 t] SELF -ENERGIZING DISK BRAKE FORAUTOMOTIVE VEHICLES [72] lnventor: Hansherger Powilleit,Erkrath-Unterbach, Germany [73] Assignee: International HarvesterCompany,

Chicago, Ill.

[22] Filed: June 11, 1970 [2l] App]. No.: 45,454

[52] US. Cl. ..l88/7l.4, l8 8/72.2, l92/70;l49

[51] Int. Cl "F1611 55/04 [58] Field of Search ..188/1 B, 71.4, 72.2,73.5; 192/70, 70.17, 149, 109 R [56] 7 References Cited UNITED STATESPATENTS 3,543,886 12/1970 Campbell ..l88/7l.4

3,548,984 12/1970 ROOt l92/70.17

3,512,614 5/l970 Powilleit et al. 192/70 1 Sept. 26, 1972 PrimaryExaminer-George E. A. l-lalvosa Attorney-Floyd B. Harman [5 7] ABSTRACTA self-energizing disk brake having a pair of thrust plates positionedwithin a stationary housing and between brake disks connected to a shaftto be decelerated. An actuating means to rotate the plates relative toeach other to cause spherical balls trapped in complementaryindentations in the facing surfaces of the plates to push the platesapart against the bias of a spring means into frictional engagement withthe brake disks. Centering cams and lugs on the plates are capable ofselective engagement with guide surfaces and projections formed on thehousing. The cams and lugs are provided with yieldable vibrationdampening elements having a low coefficient of friction to minimize theaxially directed forces resisting separation of the plates.

3 Claims, 2 Drawing Figures PATENTEDSEP26 I972 INVENTOF? HANSHERGERPOWlLLE/T ww ATT'Y SELF -ENERGIZING DISK BRAKE FOR AUTOMOTIVE VEHICLES kCROSS REFERENCE TO RELATED APPLICATION This application is related to acopending application of Hansherger Powilleit and Edmund Dohr, Ser. No.733,875 filed June 3, 1968, now US. Pat. No. 3,512,614, entitledSELF-ENERGIZING DISK BRAKE FOR AUTOMOTIVE VEHICLE and assigned to theassignee of this application.

BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to diskbrakes of the kind in which two cooperating thrust plates areaccommodated within a stationary housing in parallel relationship withone another. The thrust plates are located between the brake disks whichare connected to a shaft to be decelerated, and balls are located inconical or inclined recesses or depressions in the adjacent faces of thethrust plates. The application of the brake is initiated by rotating theplatesrelative to each other which causes the balls to urge the platesapart until they are in frictional engagement with the brake disks. Theplates then tend to rotate with the rotating member i.e., the shaft andthe brake disks attached thereto, until one plate engages with thestationary projection on the brake housing which holds it againstfurther angular movement while the frictional force, imparted to theother plate through its engagement with the brake disk, causes continuedangular movement of this other plate, which is referred to as the servoplate. This results in still further relative angular movement betweenthe thrust plates causing the balls to urge the plates still furtherapart and to thereby produce a self-energizing action to apply thebrake.

It is common practice to provide, in the brake housing, angularly spacedpilot lugs, generally three in number and spaced at equal angles aroundthe rotating shaft, extending radially inward to maintain the plates ina central position with respect to the housing, the plates being insliding engagement with the lugs. The plates also carry radialprojections which are engageable with abutment faces on a lug to form astop for one or the other of the plates according to the direction ofrotation of the shaft.

When angular movement of the plate is arrested in the application of thebrake, the plate assembly tends to pivot about the stop abutment and theplates are forced against another of the pilot lugs so that axialmovement of both plates and axial and angular movement of the energizingplate is impeded. Since this results in a tangential force on theenergizing or servo plate in a direction opposite to the rotation of theservo plate, the self-energizing effect is diminished or completelydestroyed and a greater effort has to be applied by the operator to thebrake pedal.

During the normal operation of disk brakes of the kind described, thebraking operation itself affects a centering action between the twothrust plates by means of the expander balls which are located in therecesses on the thrust plates. Consequently, there are two centeringactions which may take place; the centering of the thrust plates withrespect to one another by means of the balls located in the recesses,and the centering of the thrust plates within the housing by the actionof the centering cam. Where there are manufacturing inaccuracies in thediameters of the balls or the recesses in the thrust plates, orinaccuracies in the manufacture of the centering camson the thrustplates or in relation to the position of the individual center axes ofany of these parts, a double centering of the thrust plates at the guidesurfaces of the housing projections is involved. That is, the centeringcams of both thrust plates are acting to effect centering. The result ofdouble centering is to create tangential and radial forces and,consequently, high frictional forces which act against or destroyself-energization and thereby considerably reduce the brake effort Theseradial and tangential forces have been largely eliminated, or at leastsubstantially reduced, by the structure disclosed and claimed in theaforementioned cross referenced application.

It has been found subsequently that the inner frictional forces existingin the disk brake can be reduced still further if, in addition to thetangential and radial forces, the axial forces acting on the thrustplates can also be reduced. The axial forces are caused by contactbetween the guide faces and to some extent the housing projections, whenthe thrust plates are expanded axially.

It is, therefore, an object of the present invention to provide a diskbrake of the kind described in which a substantial reduction inundesirable frictional forces is obtained without abandoning areasonably exact control of the braking effort.

lt is also an object of the present invention to provide a disk brake ofthe kind described wherein the forces acting in an axial directiontending to resist separation of the thrust plates is substantiallyreduced.

These and other objects of the present invention will be more readilyapparent upon a perusal of the following description and theaccompanying drawings, wherein:

FIG. 1 is a section view of the braketaken transverse to the shaft to bebraked thereby, and

FIG. 2 is a cross section taken on lines I-I-ll of FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, thereis shown a disk brake of the kind described which is suitable forinstallation, for example, in the rear axle housing of a tractor. Ashaft 1, which may be a tractor axle, is mounted for rotation within ahousing 2, and has a pair of disks 3 and 4 retained on the shaft; eachdisk having brake linings 5 and 6.

Two thrust plates 7 and 8 are located between the brake disks 3 and 4,and opposing complementary recesses 9 and 10 are provided on the innerfaces of the thrust plates 7 and 8. Each pair of opposing recesses 9 and10 contains a spherical ball 11. Thrust plates 7 and 8 are normallydrawn toward each other by means of the springs 11', and the recessescontaining the balls cause the thrust plates 7 and 8 to be centered withrespect to each other. The housing 2 has three equiangularly spacedhousing projections or lugs 12, 13 and 14 for guiding the thrust plates7 and 8. In order to assist this guiding action, each of the thrustplates 7 and 8 has, on its circumference, three corresponding centeringearns 15 and 16, respectively. Two of the three housing projections,namely, the housing projections 12 and 14, simultaneously constitutestops for the lugs 19 and 20, respectively formed on the thrust plates 7and 8. Connected to the lugs 19 and 20 are the outer ends of two togglelevers 21 and 22. The inner ends of the toggles 21 and 22 are pivotallyconnected to each other and to a pull rod 23. Pull rod 23 extendsthrough the housing 2 and is connected to a brake pedal, not shown onthe drawings, for manipulation by the operator.

When the disk brake is operated, the brake pedal is depressed so as todirect the pull rod outwardly with respect to the housing 2. The togglelevers 21 and 22 therefore rotate the lugs 19 and 20 toward each other,and thus cause the thrust plates 7 and 8 to turn relative to each otherso that the balls 11 run up on the incline of the recesses 9 and 10.Thrust plates 7 and 8 are thereby forced away from one another againstthe bias of the springs 11. Axial expansion or displacement of thethrust plates 7 and 8 takes place and the actual braking effect isobtained by the thrust plates 7 and 8 engaging with the brake linings onthe brake disks 3 and 4.

Axial movement of the plates will be resisted by frictional forcebecause the stationary plate is in contact with one of the guidesurfaces and one of the projections. In order to minimize thisfrictional force resisting axial movement,'a yieldable, vibrationdampening element 24 is secured to at least the guide surface 14' of theprojection 14 and to the guide surface of projection 12. Each element 24consists of an outer metal strip or layer and an inner layer of rubber,for example, which inner layer is fastened to the guide surface and theouter layer by means of. vulcanizing or gluing. The inner layer iselastic and yieldable while the outer layer provides a low coefficientof friction material in contact with the thrust plate. Hence, the axialfrictional forces arising due to the radial motions of the thrust platesare minimized because the coefficient of friction is low and alsobecause the yieldable nature of the inner layer can smooth the radial ornormal forces, which fluctuate widely when chatter occurs for instance.The net result is that the frictional forces which tend to resist axialmovement of the stationary plate can be maintained at a minimum. Evenmore favorable results can be obtained if, in addition to the element 24being provided on the guide surfaces, a similar element 25 is providedat the stop face of each of the projections 12 and 14, such as indicatedat 14'.

What is claimed is:

1. In a self-energizing disk brake having a housing, a

pair of thrust plates positioned within the housing, discs positionedbetween the plates and housing and connected with a shaft to bedecelerated, said housing having a pair of radial projections each ofwhich includes a guide surface and a stop face and each of said thrustplates includes a centering cam and a lug, the centering cam and lug oneach thrust plate capable of engaging with the guide surface and stopface on one projection, the improvement comprising:

a yieldable, vibration dampening element secured to each of said stopfaces and said guide surfaces for engagement by said lug and centeringcam respec- 2. A disk brake according to cla1m 1 wherein said elementcomprises an outer metal layer and an inner layer of rubber.

3. A disk brake according to claim 2, wherein the rubber layer isvulcanized to the outer layer and to the housing.

1. In a self-energizing disk brake having a housing, a pair of thrustplates positioned within the housing, discs positioned between theplates and housing and connected with a shaft to be decelerated, saidhousing having a pair of radial projections each of which includes aguide surface and a stop face and each of said thrust plates includes acentering cam and a lug, the centering cam and lug on each thrust platecapable of engaging with the guide surface and stop face on oneprojection, the improvement comprising: a yieldable, vibration dampeningelement secured to each of said stop faces and said guide surfaces forengagement by said lug and centering cam respectively.
 2. A disk brakeaccording to claim 1 wherein said element comprises an outer metal layerand an inner layer of rubber.
 3. A disk brake according to claim 2,wherein the rubber layer is vulcanized to the outer layer and to thehousing.